Her representative confirmed the birth, but did not release further details such as the baby's name.
Uma's little daughter will be her first child with French born Arpad, who is estimated to be worth £136 million.
The baby girl will join elder siblings Maya, 13, and Levon, 10 – her mum's children from her marriage to actor Ethan Hawke.
On dad's side there are also two big brothers, Arpad Flynn Alexander and Aurelius Cy Andrea, whose mum is Australian supermodel Elle Macpherson.
Arpad won over one of Hollywood's most enigmatic blondes back in 2007. Apart from a brief split in 2009, the pair have been inseparable ever since.
Uma credits him with the happiness and contentment that she has found in life
"I have something I would really like to express about my love life," she announced during an interview with Harper's Bazaar.
"I'm happier with it now than I've been in many, many years. I’m trying to have as peaceful a personal life as possible."
It's a little princess!